Windows for heritage homes
Not sure of the best approach to upgrading your period property’s windows? Alan Tierney lets us in on the secret to getting this project right, including when to repair and when to replace
Alan Tierney explores the options available to ensure your period property doesn’t lose its charm during a renovation
Much of the history of an old building lies in its windows. Their detailing is often specific to a particular period, telling us a lot about the origins and development of the house, and has a crucial influence on its appearance – both inside and out. Because of this, it’s important to have a well thought-out window strategy for any period renovation project.
Unfortunately the importance of windows is often undervalued. An understandable desire to renovate and modernise – combined with aggressive marketing by some manufacturers – has contributed to widespread, unsympathetic replacement. This has had a very damaging effect on the character of many period houses, particularly Victorian and Edwardian terraces.
It’s self-evident that the primary purpose of a window is to allow light into the building, with ventilation as an important additional benefit. However the style, size and positioning of a home’s fenestration have always been important elements of design; and over the centuries they have reflected status, wealth, fashion and technological capability. In fact it’s not uncommon for the visual impact of windows to be more important to the appeal of a heritage building than their practical function. So let’s take a look at these factors in more detail before we investigate how you can get the right result for your project.
Status
Historically, windows were often carefully selected to express the status and wealth of the owner. Medieval open halls had large, fullheight windows to light the upper end, where the master of the house sat. Meanwhile, great Elizabethan homes had vast areas of extraordinarily expensive glass, purely for show.
When the window tax was in force during the 18th and 19th centuries, some wealthy individuals perversely increased the number of windows in their houses to show they could afford it, while others bricked them up because they couldn’t. Factors
such as this can underpin a property’s historical interest – telling a story that feeds into the building’s character, and therefore its value.
Trends
Window style was influenced by the fashions of the day. A good example is during the classical revival in the 18th century, which was concerned with form and symmetry. Windows were placed where they looked correct in the facade, regardless of how that related to the interior; they would simply be blacked out when they clashed with internal features.
In fact, the Georgians extensively remodelled the exterior walls of many existing houses so as to incorporate symmetrically arranged sash windows in place of the irregular originals. The later Victorian gothic style was a reaction to the severity and artificiality of classical architecture and made a point of locating windows where they would best light the interior. This resulted in an irregularity that was sometimes taken to excess.
Fostering an understanding of historic architectural trends and the local vernacular is therefore an important part of developing the right strategy for repairing and updating your period home’s fenestration.
Technology
Another element that has always controlled window design is glass making techniques. Early products were very thin and could only be used in small pieces, so units had leaded lights, incorporating small quarries of glass that were usually diamondshaped. In fact, glazing an aperture was very expensive and therefore rare. Instead most windows were unglazed, with wooden shutters to keep out the weather and timber or stone mullions for security.
Sash windows developed from the late 17th century, initially with very small panes and thick glazing bars. Improved technology and lower prices made it possible to have larger panes and thinner glazing bars, with single pane sashes common by the end of the 19th century. This is often where renovation projects fall down; think of the Victorian and Edwardian terraces I mentioned earlier, which now often feature a hodgepodge of unsuitable replacement glazing styles.
Keeping a home’s existing windows
If you have old windows in your house (which may or may not be the originals), retaining them will almost always be the right thing to do. A significant reason for this is that they tell a lot about the history and development of the building. What’s more, if the property is part of a larger development or terrace, they will contribute to the overall scheme and streetscape. This is one of the reasons why, if your home is listed or in a conservation area, you will need consent to change any windows.
Examples that seem to be in poor condition can usually be repaired by a skilled joiner. This is almost always better than replacement – and not just because it’s preferable to retain historic fabric, if at all possible. The wood used to make windows before the 20th century was of very high quality and is extremely durable. It’s no longer possible to source timber of that standard, although the latest composite construction methods and advanced coatings can approach the same level of performance – albeit for a premium price.
It’s also worth bearing in mind the irregularities and impurities in older glass make it much more attractive to look at, and through, than modern products. It is rarely possible to reuse glass if a window is remade.
Modern replacements
Many old windows have been swapped out for inappropriate substitutes in recent decades. Unfortunately, these are very often of poor quality, which can cause problems functionally as well as visually. The frames are frequently made of cheap softwood or low-grade PVCU, both of which have a short service life and deteriorate very quickly. Design, style and material are typically inconsistent with the character of heritage buildings, too, significantly detracting from their appearance.
Where the style of the lost windows is known (eg from photos or any remaining originals), or there is good evidence in the local area as to what might have been in situ, then the best approach is to reinstate them as accurately as possible. Of course there are limits to how far this is practical. It would obviously not be sensible to reinstate an unglazed window with timber mullions and shutters; while traditional metal leaded lights may be prohibitively expensive and will perform poorly in terms of energy efficiency. This is one of those areas where careful research, good, well-informed advice and clear, open communication with the conservation officer will provide the recipe for success.
If there is no historic template to follow or replication is not feasible,
good modern design can be very successful. The highest quality timber available is usually the best material choice for sensitive projects, though powder coated aluminium or even modern steel frames can work well in some situations.
The energy conundrum
Thermal performance is a major and increasing concern for homeowners, both for environmental reasons and in terms of keeping utility bills under control. Part L of the Building Regs (in England & Wales; see F1 in Northern Ireland and Section 6 in Scotland) requires levels of efficiency that are almost certainly far above what your existing units can achieve. If you’re undertaking a renovation, these rules will come into play, particularly if you are planning to refurbish or replace the windows. The requirements of building conservation and Part L frequently conflict, however, and if the property is listed then conservation will be the overriding priority.
When repairing an old window, it’s not possible to incorporate double glazed (DG) panels while retaining the original glazing bars (or their size and profile). This means DG is rarely appropriate in heritage fenestration. The loss of historic glass would also detract from the house’s character. In fact, some conservation officers take the view that it should never be allowed in listed buildings.
That said, there are solutions available for fitting double glazing to historic frames – using slim panels or vacuum-filled units – and these might be approved in some circumstances. Do be aware that these don’t come cheap, and their medium- to longterm performance is as yet unproven.
If you’re commissioning exact likefor-like replacements, to reinstate previously lost examples, these won’t usually look right with double glazing either. But if the project requires newly designed replacements, then carefully specified versions should be suitable in all but the most sensitive conservation situations. Again, look to use high-quality timber, powdercoated aluminium or possibly steel frame units to attain the right result in terms of profiles and sightlines – and avoid cheap PVCU versions (token efforts to incorporate fake leaded lights or glazing bars into poor quality units won’t help).
It’s worth pointing out that modern techniques aren’t the be all and end all. The thermal performance of most existing period windows can actually be cost-effectively improved using measures such as draughtproofing, secondary glazing, shutters and thick curtains. A study carried out a few years ago by English Heritage showed that a Victorian sash window, upgraded like this, can outperform a contemporary double glazed unit.